Virtual Image Display Device Diffractive Optical Element Folding Mirror
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Solution Overview
Problem
Conventional virtual image display devices for vehicles suffer from low efficiency due to light attenuation when projecting images on windshields, as the display light is transmitted and reflected multiple times, leading to reduced visibility and luminance of the virtual image.
Innovation Solution
A virtual image display device incorporating a diffractive optical element and a folding mirror, where the display light is transmitted and diffracted in different polarization states, allowing for increased optical path length and reduced light loss, enhancing the efficiency and visibility of the virtual image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the display light is transmitted and reflected multiple times through the windshield to project the virtual image, then the virtual image can be displayed on the windshield, but light attenuation occurs leading to reduced visibility and luminance
Solution Approach 1:
The patent introduces a folding mirror to create a folded optical path, effectively increasing the optical path length in a limited physical space. This allows the display light to travel a longer distance and interact more effectively with the windshield projection surface, improving image luminance without requiring a larger device footprint.
Solution Approach 2:
The folding mirror acts as an intermediary element that redirects the display light at specific angles, enabling precise control over the light path. This intermediary component helps optimize the light transmission and reflection process, reducing unnecessary light loss while maintaining the virtual image projection quality on the windshield.
2Illumination intensity
If the optical path length is increased to improve image quality, then the visibility of the virtual image is enhanced, but the device size increases
Solution Approach 1:
The folding mirror configuration transforms a linear optical path into a folded, multi-dimensional path. This allows the light to traverse a longer effective distance while the physical footprint of the device remains compact, effectively decoupling optical path length from device volume.
Solution Approach 2:
The optical components including the folding mirror, diffractive optical element, and display unit are arranged in a nested, space-efficient configuration. The folding mirror is positioned to utilize the space between other components, creating a compact integrated assembly that achieves long optical path length without proportional increase in device volume.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The configuration significantly improves the efficiency of the virtual image display by minimizing light attenuation and enabling the display of a larger virtual image within the constraints of the device size, ensuring high visibility and luminance for the occupant.
Implementation Method 1
The optical element is configured to exert an optical action on the display light
Implementation Method 2
the display light is transmitted and diffracted in different polarization states
Implementation Method 3
the folding mirror is provided on an opposite side of the diffractive optical element from the display unit and is configured to reflect the display light
Data Source
AI summary
A diffractive optical element exerts a diffractive action on a display light that is emitted from a display unit. A folding mirror is provided on the opposite side of the diffractive optical element from the display unit to reflect the display light. The diffractive optical element includes a transmissive action part and a diffractive and reflective action part. The transmissive action part exerts a transmissive action to transmit therethrough the display light, which is incident from the display unit and is in a first polarization state, toward the folding mirror. The diffractive and reflective action part exerts a diffractive and reflective action to diffract and reflect the display light, which is reflected by the folding mirror and is in a second polarization state opposite to the first polarization state, toward the projection portion on an optical path.